Apparatus for cold-drawing yarn



Jan. 15, 1963 R. L. KROLL 3,073,001

APPARATUS FOR COLD-DRAWING YARN Filed Oct. 21.. 1958 Hial- APPARATUS FOR Robert L. Kroll, Kinston,

de Nemours and Company,

poration of Delaware Filed Oct. 21, 1958, Ser. No. 768,651

3 Claims.

This invention relates generally to the art of forming artificial filaments and, more particularly, to the colddrawing of yarn consisting of one or more filaments, each composed of synthetic linear polymers.

Linear polymers can be formed directly into filaments from the molten state and the filaments so formed are capable of being cold-drawn, i.e., permanently elongated, in the solid state at any temperature below the melting point, under the application of stress, into filaments and the like exhibiting, upon X-ray examination, crystallite orientation along the fiber axis. These cold-drawn and oriented filaments possess certain characteristics of uniformity not possessed by undrawn filaments. Such physical characteristics generally can be obtained only through uniform drawing of the filaments. Inasmuch as the cold-drawing of synthetic linear filaments may effect an increase in length many ments and a decrease in elongation to a small fraction of that possessed by the undrawn filaments (filaments of polyhexamethylene adipamide, a linear polyamide obtainable from the reaction of hexamethylene diamine and adipic acid, for example, being capable of being colddrawn on the order of several hundred percent with an accompanying reduction in elongation to about 20%), it is important that variations in physical characteristics along the length of the filaments which occur during cold-drawing be maintained within small limits. A great improvement in the uniformity of drawn yarns followed the introduction of devices to localize the drawpoint, such as the draw pin disclosed in U.S. Patent No. 2,289,232.

Even the use of the draw pin does not prevent the occasional occurrence of a non-homogeneous section along the filament. These non-homogeneous sections of filament may have a length of about one-half to about twenty times the filament diameter. The non-homogeneity may be a nub having a diameter considerably larger than the average diameter of the yarn, a higher spinning birefringence, or an impurity. These non-homogeneities not only detract from the appearance of fabric made from the filaments, but also are the cause of broken filaments, draw roll wraps, and other instances of poor process operability which, in turn, result in loss of product and production time.

The most important object of this invention is the provision of a process and apparatus for producing uniformly cold-drawn synthetic linear polymer yarns and filaments.

Another important object of the invention is the provision of uniformly cold-drawn synthetic linear polyamide yarns and filaments.

A further object of the present invention is to provide a process and apparatus for continuously and uniformly cold-drawing synthetic linear polymer yarns and filaments with improved process operability.

With these and other objects in view, the apparatus of the present invention includes structure for carrying out the feeding, snubbing, and drawing steps of a cold-drawing process, which apparatus has been modified either by the addition of yarn diverting means, by the relocation of the draw pin, or by a combination of these features. Such modifications and the advantages inherent therein will be described herein, with reference to the accompanying drawing, wherein:

times that of the undrawn fila' 3,fi73,fifil Patented Jan. 15, 1963 FIGURE 1 is a schematic representation of a preferred embodiment of the drawing apparatus of the present invention;

FIG. 2 is a FIG. 1; and

FIG. 3 is a schematic representation of an alternate form of apparatus useful in the practice of the invention.

The expression process operability refers to the frequency with which the thread line breaks down and, in the drawing of multi-filament yarns, to the number of broken filaments which form so-called draw roll wraps and result in bobbin rejects.

According to the teaching of the present invention, when the distance from the draw pin to the point of tangency between the filament and the draw roll, i.e., the draw zone, is materially increased, a more uniform yarn is obtained and substantially better process operability is achieved. This distance, which is about 4 /2 inches in conventional cold-drawing processes, is increased to a distance ranging from 8 to 40 inches, and preferable from 12 to 35 inches.

Referring now to FIG. 1, a cold-drawing apparatus has been illustrated which includes a feed section 10, a draw pin 12, a draw section 14, and a balloon which the yarn passes to a windup bobbin.

The feed section 19 includes a rubber-covered pinch roll 16 and a feed roll 18. Yarn 2% from a creel (not shown) passes through one throat of a double throat guide 22, over pinch roll 16, onto feed roll 18, and is diverted upwardly by its passage through the second throat of guide 22 to the draw pin 12. The yarn 2G is passed about the draw pin several turns, so as to localize the draw point at the pin. The pin 12 is mounted at an angle, as shown, so that successive turns thereabout will remain separated.

The draw section 14 includes a draw roll 26 and a separator roll 28, over which the yarn is trained before passing to the guide 30. in FIG. 2, it is seen that yarn 20 makes several passes over the rolls 26 and 28, the peripheral speed of which may be anywhere from 1 /2 to 10 times that of the feed roll, depending on the draw ratio that is desired.

in operation, the yarn 29 is fed at a uniform rate by the feed roll 13 to the draw pin 12, via the second throat of guide 22 which functions to divert the yarn away from'the roll 18 so that the draw pin 12 may be located at a substantially greater distance from the draw roll 25, resulting in a draw zone within the desired range.

In FIG. 3, an alternate embodiment of the apparatus is illustrated in which the yarn 20 from a creel makes several wraps about roll 16' and a multiple grooved guide 17' before passing over feed roll 18' to a conventionally located draw pin 12'. The multiple grooved guide 17' facilitates more than one wrap around the pinch roll 16'; such multiple pinching is preferred where heavy denier yarn is being handled. A roller guide 24 is positioned on the apparatus beneath the roll 18 and away from the normal path of travel of the yarn between draw pin 12 and draw roll 26'. In this manner, substantially the same results are achieved, i.e., the draw zone is extended to a length that is within the desired range of the present invention.

The efficiency of these arrangements is independent of the distance between the feed section and the draw pin, so long as a sufiicient number of turns is taken about the draw pin and no appreciable tension exists in the yarn upstream therefrom, as compared to the section between the draw pin and the draw roll.

In actual operation, under various operating conditions, several examples of the improvements to be expected from the application of this invention have been recorded.

detailed view of the draw rolls shown in guide 30 through 'mentinspection rejects, and a 30% Example I 15 denier monofilament yarn of polyhexamethylene adipamide (66 nylon) was drawn at 500 yards per min- 4 /2 inch distance between pin and draw roll there was approximately one nub for every 1300 yards. When the draw pin was moved very close to the draw roll /2 inch distance), the average spacing between nubs became about 25 yards, but if the distance between pin and roll was increased to 9 inches, no nubs were encountered in 75,000 yards.

Example II When drawing filaments of polyhexamethylene adipamide (66 In the former case only 3% of the positions showed draw roll wraps as compared to 7% in the latter case.

Example III The installation of raised draw pins so as to give a 15- inch draw zone (instead of 4 /2 inches) allowed increasing the spinning speed (and hence machine productivity) for 15 denier monofilament yarn by 25% while maintaining the same quality standards as were kept at the slower speed.

Example IV High tenacity yarn consisting of 140 filaments of 66 nylon was drawn at a draw ratio of 4.8 to a drawn denier per minute, using a 24-inch draw roll wraps was decreased from 73% to 17%, the number of draw twister breaks from 7 per 1000 pounds to 6 per 1000 pounds, and the number of bobbins rejected for broken filaments was decreased from 5.7 to 3.4%.

Example V In the drawing of 15 denier monofilament nylon yarn spun at 450 yards per minute and then drawn at a draw and 30. Optimum results were obpin 21 inches from the point of tangency to the draw roll which resulted in 1.8 nubs per 1000 yards.

Example VI 7 In an extended test using 1872 draw twister positions operating at a drawing speed of 269 yards per minute in which a 24-inch, draw zone was employed between draw reduction in quality stops per beam were achieved.

A theoretical explanation of the striking improvements in yarn uniformity and process operability achieved by extending the draw zone is as follows: if a filament section of length y contains a non-homogeneous draw-resistdraw ratio at is applied to this section, the total length of the section of filament after drawing will be z=yx. Since the non-homogeneous x and x should be kept to a minimum. Increases in this difference (x,x) will increase the probability of a filament breakdown. The term (x,-x) has a high value when the draw zone is short and the nontion of this zone. By extending the draw zone, the fraction of this zone occupied by the non-homogeneous segment is relatively small and the term (Ja -x) has a low value. However, when the draw zone is extended beyond although it will be understood that the invention is equally applicable to other fiber-forming polyamides and other fiber-forming polymers such as synthetic linear polyesters.

I claim:

1. Apparatus for cold-drawing yarn, said apparatus comprising: a source of yarn, a feed roll receiving yarn pin and the draw roll defining a draw Zone, and fixed guide means for diverting the path of References Cited in the file of this patent UNITED STATES PATENTS 

1. APPARATUS FOR COLD-DRAWING YARN, SAID APPARATUS COMPRISING: A SOURCE OF YARN, A FEED ROLL RECEIVING YARN FROM THE SOURCE, A DRAW ROLL FOR RECEIVING YARN FROM THE FEED ROLL, A FIXED DRAWN PIN FOR SNUBBING THE YARN AS IT PASSES FROM THE FEED ROLL TO THE DRAW ROLL, THE LENGTH OF THE YARN PATH OF TRAVEL BETWEEN THE DRAWN PIN AND THE DRAW ROLL DEFINING A DRAW ZONE, AND FIXED GUIDE MEANS FOR DIVERTING THE PATH OF TRAVEL OF THE YARN INTERMEDIATE THE ROLLS WHEREBY TO PERMIT AN EXTENSION OF THE DRAW ZONE, SAID ZONE BEING FROM 12-35 INCHES IN LENGTH. 